As power and power density requirements of a heater chip of a thermal ink jet printer have increased, operating temperatures of the ink cartridge have reached unacceptably high levels. As the speed of operation increases, the temperature of the ink cartridge rises.
Without a cooling arrangement, unacceptably high operating temperature levels may be reached on the heater chip. For example, it is desired that the heater chip have a maximum temperature below 20.degree. C. above room temperature and have a temperature range of between 10.degree. C. and 50.degree. C. above room temperature.
When the heater chip becomes too hot, its reliability decreases. This includes degradation in print quality.
Accordingly, various cooling arrangements have been suggested for removing waste heat from the heater chip and for keeping the heater chip temperature in a satisfactory range while operating at faster speeds. These cooling arrangements have usually been active cooling devices.
The active cooling devices have typically been forced convection devices requiring fluid pumping with the source of the fluid pumping being a force external to the cartridge. One example of an active cooling device having a pump is disclosed in U.S. Pat. No. 5,084,713 to Wong.